*{
    margin: 0;
    padding: 0;
}
a{
    text-decoration: none;
    color: #9a9a9a;
}
html,body{
    width: 100%;
    height: 100%;
}
#box{
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, .1)
}
ul,li{
    list-style: none;
}
.nav-box{
    width: 210px;
    height: 100%;
    margin-top: 50px;
    background: #282828;
}
.nav-box ul li {
    width: 210px;
    height: 50px;
    line-height: 50px;
    border: 1px solid green;
    
}
.nav-box ul li .aaa{
    display: flex;
}
.nav-box .aaa span {
    display: block;
    flex: 9;
    margin-left: 10px;
}
.nav-box .aaa i {
    display: block;
    flex: 1;
    margin-right: 5px;
}